Rocha E.P.,Sao Paulo State University |
Anchieta R.B.,Sao Paulo State University |
de Almeida E.O.,Sao Paulo State University |
Freitas A.C.,Sao Paulo State University |
And 4 more authors.
Computer Methods in Biomechanics and Biomedical Engineering
Veneer fracture is the most common complication in zirconia-based restorations. The aim of this study was to evaluate the mechanical behavior of a zirconia-based crown in a lower canine tooth supporting removable partial denture (RPD) prosthesis, varying the bond quality of the veneer/coping interface. Microtomography (μCT) data of an extracted left lower canine were used to build the finite element model (M) varying the core material (gold core – MAu; zirconia core – MZi) and the quality of the veneer/core interface (complete bonded – MZi; incomplete bonded – MZi-NL). The incomplete bonding condition was only applied for zirconia coping by using contact elements (Target/Contact) with 0.3 frictional coefficients. Stress fields were obtained using Ansys Workbench 10.0. The loading condition (L = 1 N) was vertically applied at the base of the RPD prosthesis metallic support towards the dental apex. Maximum principal (σmax) and von Mises equivalent (σvM) stresses were obtained. The σmax (MPa) for the bonded condition was similar between gold and zirconia cores (MAu, 0.42; MZi, 0.40). The incomplete bonded condition (MZi-NL) raised σmax in the veneer up to 800% (3.23 MPa) in contrast to the bonded condition. The peak of σvM increased up to 270% in the MZi-NL. The incomplete bond condition increasing the stress in the veneer/zirconia interface. © 2014, © 2014 Taylor & Francis. Source
Medina-Macedo L.,Federal University of Parana |
Medina-Macedo L.,Technical Federal University of Parana |
Sebbenn A.M.,University of Sao Paulo |
Lacerda A.E.B.,EMBRAPA Forestry Brazilian Agriculture Research Corporation |
And 3 more authors.
Tree Genetics and Genomes
In this study, genetic diversity, inbreeding, spatial genetic structure (SGS), and pollen dispersal are analyzed using ten microsatellite loci from two populations of the dioecious, wind-pollinated, coniferous tree Araucaria angustifolia in Southern Brazil. The study populations include an undisturbed 7 ha A. angustifolia cluster, where all adult trees were mapped and sampled, and an adjacent, long-abandoned, open agricultural area with an aggregated A. angustifolia population. Seeds were collected from 13 seed trees inside the forest cluster and from eight seed trees in the open forest. Our results showed that the adults present high levels of heterozygosity (Ho = 0.91) and an absence of inbreeding. However, significant SGS was detected up to 90 m in the forest cluster suggesting that near-neighbor trees are related. The estimate of effective population size was lower than the total number of trees in the cluster (Ne/N = 0.19), which can be explained by the presence of SGS in the stand. Substantial external pollen flow was detected in the forest cluster (26 %) and open forest (20 %), indicating that the reproductive population size is greater than the sampled populations, explaining the high genetic diversity in this population. Our results indicate that this site has potential for in and ex situ conservation due to high levels of genetic diversity and gene immigration resulting from pollen flow. Conservation strategies for A. angustifolia should focus not only on forest fragments but should also include the preservation of isolated trees throughout the landscape. © 2014, Springer-Verlag Berlin Heidelberg. Source